1. Field of the Invention
The present invention relates to a one-coat aqueous adhesive for bonding castable urethanes to various metals during the molding cycle of the urethane, and comprising a phenoxy resin plus a phenolic resole resin.
2. The Prior Art
Volatile organic compounds (VOC's) have been under strict governmental regulations which are getting stricter. The use of organic solvent-borne adhesives for bonding castable urethane-to-metal substrates is no longer desirable; and aqueous adhesive systems have become more desirable in order to reduce the VOC's so as to abide by these strict regulations. By using a VOC-compliant aqueous adhesive, it is possible to bypass expensive solvent-handling problems.
Examples of aqueous adhesive compositions are as follows.
Jazanski et al., U.S. Pat. No. 4,167,500, discloses storage-stable, heat-reactive aqueous compositions comprising at least one novolak phenolic resin, at least one formaldehyde polymer, and water, wherein the formaldehyde polymer is present in an amount sufficient to crosslink the novolak resin.
Sadowski U.S. Pat. No. 4,483,962 discloses terpolymer latexes prepared by emulsion polymerization of 2,3-dichloro-1,3-butadiene and a mixture of at least two different unsaturated monomers, with these unsaturated monomers being at least individually copolymerizable with 2,3-dichloro-1,3-butadiene, adhesive systems.
Auerbach et al., U.S. Pat. No. 5,036,122, discloses an adhesive composition for bonding metal to natural or synthetic rubber, composed of a latex, an aromatic nitroso compound, and a polymaleimide compound.
Warren U.S. Pat. No. 5,200,455 discloses an aqueous primer composition containing a polyvinyl alcohol-stabilized aqueous phenolic resin dispersion, a latex of a halogenated polyolefin, and a metal oxide. The phenolic resin dispersion is prepared by mixing (a) a pre-formed, solid substantially water-insoluble, phenolic resin; (b) water; (c) an organic coupling solvent; and (d) polyvinyl alcohol, at a temperature and for a period of time sufficient to form a dispersion of the phenolic resin in water.
Weih et al., U.S. Pat. No. 5,200,459 discloses a butadiene heteropolymer latex prepared by emulsion polymerizing appropriate monomers in the presence of polyvinyl alcohol and a stabilizing solvent. The butadiene heteropolymer can be a butadiene copolymer or terpolymer prepared from butadiene monomers and comonomers such as .alpha.-haloacrylonitrile and acrylic acid.
Mowery U.S. Pat. No. 5,281,638 discloses an aqueous adhesive composition containing a chlorosulfonated polyethylene latex, a polymaleimide compound, a nitroso compound and a metal oxide.
Weih et al., U.S. Pat. No. 5,300,555 discloses a butadiene homopolymer latex prepared by emulsion polymerizing appropriate monomers in the presence of polyvinyl alcohol and a stabilizing solvent. The butadiene homopolymer lattices can be prepared without problem of coagulation and can be utilized effectively in adhesive compositions without the use of volatile solvents.